1. Field of the Invention
The present invention relates to novel compositions of matter and methods of using said compositions. More particularly, it relates to compositions of matter useful as mold release and parting agents for protecting and lubricating the surfaces of molds, plungers, and other article-forming parts, especially such as are useful in the manufacture, forming, and handling of glass articles or the like at high temperatures.
2. Description of the Prior Art
Before situating new molds into use, the glass industry has generally adapted the process of using various compositions applied to the mold-forming surfaces. While these compositions and methods of application have been successful as a preliminary treatment, many difficulties have been observed in the subsequent treatment of the molds during operation in the molding machines.
In glass manufacturing, a glob of molten glass is formed by a blank mold into the parison having a finished portion corresponding to the neck portion of the desired glass article. It is a requirement that the molding surface of the blank mold not become abraded or pitted so that the molten glass will readily flow over the molding surface of the mold, take the shape thereof, and then separate therefrom. As can be appreciated, this process creates a dragging or abrasive effect upon the molding surface of the glass-forming equipment. While the working temperatures of the glass-forming machine may vary from about 500.degree. to 1000.degree.F., in the glass industry, it often reaches 1200.degree.F. Generally, during the final process of shaping and forming, the molten glass is allowed to cool to a temperature between about 1250.degree.F., to 1350.degree.F. Therefore, any molds and release compositions must be compatible with and effective at these temperatures.
Several practices have been followed in the past for the protection and lubrication of such molds used in forming glass articles. The common practice in most cases in the glass factories has been to use for this purpose a compound of bulk of which consists of light paraffin base oil and containing graphite in suspension, in most cases in the glass factories. These light paraffin base oils are numerous in kinds and such hydrocarbons as kerosene have been employed. Generally, these compositions are applied by spraying, painting, or swabbing during the forming operation so as to provide lubrication of the interacting mold sections to prevent sticking of the molten glass to the mold surfaces. While the spray of oil carrying the lubricant such as graphite may be used at these temperatures, there are many important objections to the use of the light paraffin base oil. It is used primarily as a carrier for the graphite and quickly volatilizes on the hot surfaces of the molds. Thus, it will be appreciated that this presents drawbacks in such compositions containing these oils as well as their method of application. Aside from the obnoxious odors, the vaporized materials create considerable volumes of smoke which reduce visibility, and produce upon condensation serious fire hazards which oftentimes become progressively worse as the accumulation increases. Further, as a result of the evaporation of so much oil from the glass-forming surfaces, there is a tendency for hard carbon deposits to build up on such mold surfaces thus producing inferior glassware and even more serious troubles. It should be added that the storage of the necessary substantial quantities of oil is a nuisance in a glass factory and of course the cost of the oil is a considerable item. The application of these conventional compositions to various moving parts of the machine in actual production must be regularly repeated a number of times on a periodic basis which could result in injury to operators. Needless to say, these problems have required that the industry employ other solutions to circumvent these undesirable conditions. Further discussions of the long existing problems with such compositions and efforts to avoid these problems can be found in U.S. Pat. Nos. 3,141,752; 3,480,422; 3,508,893; 3,523,016 and 3,623,556.
Because of these objections to the use of paraffinic materials various attempts have been made to use a solution or suspension of a lubricant in an aqueous system. A number of aqueous systems have been employed with various degrees of success. While such a solution is useful in the preliminary treatment where the application is made at temperatures substantially lower than 500.degree.F., it has not been found satisfactory for use during subsequent treatment where the mold temperature is necessarily higher, usually over 825.degree.F. This is due to the fact that the small drops of water striking the hot surfaces are converted into steam with almost explosive violence, carrying with it mechanically the lubricant which has been in solution or suspension in the water. Thus, instead of adhering to the mold surface, most of the lubricant falls away and is wasted. The use of various binders which resolve this problem by fusing and bonding the lubricant to the moldforming surface have been suggested. Because of the rigorous operating conditions and high temperatures encountered in glass-forming operations, numerous compositions employing lubricants in conjunction with various binders have only been moderately utilized by those skilled in the art. The subject invention deals with one approach for precoating molds and molding parts with an aqueous dispersion, especially applicable to the glass-forming machines.